1. Field of the Invention
The present invention relates to imaging apparatuses. More specifically, the present invention relates to an imaging apparatus having an autofocus (AF) function and to a method for controlling the imaging apparatus.
2. Description of the Related Art
In recent years, imaging apparatuses to capture images of subjects including people and record the images as captured image data, such as digital video cameras, have been widespread. As this type of imaging apparatuses, many imaging apparatuses having an AF function to automatically focus on a subject have been suggested.
For example, there has been suggested an imaging apparatus to perform AF control by detecting a contrast signal from captured image data and specifying an in-focus position based on a signal level of the contrast signal. In this AF control method, it is determined that an in-focus level is higher as the signal level of the contrast signal (AF evaluation value) is higher, and focus control is performed by moving a focus lens to the position where the largest AF evaluation value can be obtained. According to this AF control method, an in-focus position can be specified by using captured image data converted by an imaging device, and thus it is unnecessary to provide a ranging optical system other than an imaging optical system in the imaging apparatus. For this reason, the AF control method has been widely used in digital still cameras and the like in recent years.
Also, there has been recently suggested an imaging apparatus capable of detecting a face from a captured image, setting an area serving as an AF target onto the face in the captured image based on information about the detected face, and appropriately focusing on the face in the captured image. Also, there has been suggested an imaging apparatus to set a driving range of a focus lens based on a face detected from a captured image.
For example, there has been suggested an imaging apparatus to detect information of a face of a subject from captured image data, estimate the distance to the subject (subject distance) based on the detected information of the face, and change a driving range of a focus lens in accordance with the subject distance and a depth-of-field (e.g., see Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-18246 (FIG. 1)).